Well open source CAN and MII implementations do exist. Perhaps you can help provide a pull request to the official repo that checks in appropriate versions of that code, or file an issue requesting them to do it.
My biggest issue with their wireless implementation is that I get my boards made at JLCPCB and Raspberry Pi chose a specialty wireless chip for the Pico W which is not widely available, and is not available at JLCPCB.
https://github.com/KevinOConnor/can2040
https://github.com/sandeepmistry/pico-rmii-ethernet
My biggest issue with their wireless implementation is that I get my boards made at JLCPCB and Raspberry Pi chose a specialty wireless chip for the Pico W which is not widely available, and is not available at JLCPCB.